DISEASE CHARACTERISTICS: Immunohistochemically confirmed p185-HER2 expressing stage IIIB (pleural effusions only) or IV non-small cell lung cancer Confirmed overexpression at least: 1+ p185-HER2 (by DAKO Hercep Test) OR 15 ng/mL serum HER2/neu shed antigen (by Human HER2 Quantitative ELISA) At least 1 site of measurable disease outside of prior radiation port Brain metastases allowed provided clinical neurologic status is stable and head CT scan is stable to improved